The purpose of this study is to determine the long-term performance of implanted lower extremity neuroprostheses for individuals with mobility impairments due to paralysis. Implanted functional electrical stimulation (FES) systems to restore standing and walking function have been installed in more than two dozen volunteers in various VA-sponsored research projects over the past two decades. In the short term, implanted lower extremity motor system neurorpostheses enable users to stand to retrieve and manipulate objects and negotiate spaces inaccessible to the wheelchair, improve general health, reduce secondary medical complications, and elicit high degrees of satisfaction and usage. The long-term reliability of the implanted components and clinical performance of the neuroprostheses need to be evaluated to determine whether these acute benefits are maintained chronically. In this retrospective study we will a) collect longitudinal data on the clinical and technical performances of implanted neuroprostheses for standing and walking after paralysis, and b) provide the technical support necessary to maintain the functional gains achieved with the initial application of the neuroprosthesis. The experimental design will take the form of a series of multiple-baseline case studies in which subjects act as their own historical controls for post-implant and long-term follow-up assessments of recruitment stability, component reliability, functional capacity, satisfaction, patterns of usage, health status and societal participation. A cohort of former recipients of implanted lower extremity neuroprostheses will be contacted, interviewed and brought to our laboratory for physical examination, collection of physiological and technical data, and long-term functional and clinical follow-up assessment. The resulting data will definitively determine whether the acute outcomes of neuroprosthetic interventions previously reported are retained long-term, establish the chronic safety and stability of the systems, and elucidate the manner in which the technologies are incorporated into the lives of their users. This project provides the VA with a unique opportunity to both collect original data regarding the chronic, longitudinal performance and clinical utility of the technologies that it developed and disseminated, as well as to perform the routine system maintenance required to keep the neuroprostheses operational and allow their users to retain their restored function for as long as possible.